Wood adhering machine



June 7, 1949. J, w, JONES, ,R 2,472,708

WOOD ADHERING MACHINE Filed May 2, 1946 INVENTOR Jb/wv M750/v n/5.5', 'c7.

ATTORNEY Patented June 7, 1949 WOOD ADHERING MACHINE John Watson Jones, Jr., Los Angeles, Calif., assignor to Radio Corporation of America, a corporation of Delaware Application May 2, 1946,v Serial No. 666,611

This invention relates to high frequency heating systems, and particularly to a high frequency system for gluing a number of elements, such as wood beams, either at predetermined points,

called spot gluing, or over the entire length of' the composite beam.

. The use of high frequency current for setting glue is well-known, reference being made to stephen U. s. Patent No. 2,231,457 of February lfl, 1941, while a spot gluing system for the edges of lumber is disclosed and claimed in Linquist Il. S. Patent No. 2,317,281 of April 20, 1943. The present invention, however, is directed to an lmproved system of directing the heating currents eiciently through a, large synthetic timber beam made up of multiple parts in which the abutting surfaces or glue lines run in planes at angles to one another, particularly at right angles. For instance, in the edge gluing process disclosed by Linquist, two electrodes are placed directly on the glue line or abutting surfaces of the boards so that the high frequency currents pass directly into the glue, since the electrodes are in contact therewith. Since the boards are comparatively thin, the field is uniform within the glue between electrodes?. In a large timber made up of a plurality of narrow pieces of different cross-sections, or a round hollow or solid pillar, it is realized that some of the glue lines will run at various angles to other glue lines. Electrodes placed on opposite sides of a square or rectangular timber do not permit the efficient heating of glue along all glued surfaces, especially at right angles to the direction of the eld. Furthermore, it has been found that the provision of a linear varying potential gradient between electrodes increases the heating eflciency by high frequency and thus shortens the heating period necessary to set the glue.

n The arrangement of the electrodes in the present invention, therefore, permits the currents to flow directly into the glue lines regardless of their position, and the electrodes are so formed as to provide a uniform field between the high potentialand grounded electrodes. Thus, the heating of all glue throughout the cross-section of the timber at the spot being glued is uniform and simultaneous. Thus, the spot gluing method disclosed by Linquist is made effective for the making of large dimensloned beams of differently shaped cross-sections.

`Thel principal object of the invention, therefore, is to facilitate the gluing together of small strips of lumber to produce a large beam.

Another object of the invention is to improve 4 Claims. (Cl. 21.9-47) the high frequency heating efficiency of glue along surfaces at angles to one another.

, A further object of the invention is to provide an improved electrode system for eiiiciently applying high frequency energy to an element having glue lines running at right angles to one another.

A still further object of the invention is to provide an electrode system in which a uniform field is provided throughout the dimensions of a wooden timber.

Although the novel features which are believed to be characteristic of this invention will be pointed out with particularity in the appended claims, the manner of its organization and the mode of its operation will be better understood by referring to the following description read in conjunction with vthe accompanying drawings, forming a part hereof, in which:

Fig. l is a perspective View of two forms of electrodes applied to a rectangular or square Wooden timber made up of smaller strips.

Fig. 2 is a diagrammatic arrangement showing the connections between the high frequency generator and the electrodes, and

Fig. 3 is a cross-sectional view taken along the line 3--3 of Fig. 2.

Referring now to the drawings, in which the same numerals identify like elements, it will be noted that a plurality of wood strips 5-l2, inclusive, of different cross-sections have been fitted together to form a large beam l' having a cross-section which is approximately square, although the invention is similarly applicable to a rectangular beam of any dimension. The invention may also be used for hollow or solid pillars or columns, the electrodes being shaped to the external form of the article. The contacting surfaces between the parts 5-I2, inclusive, are coated with glue, and they are held together by clamps, such as shown at I5 and l?. As explained in the above-mentioned Linquist patent, after the glue, at a spot along the timber, has been properly set by high frequency, the clamps may be removed and the heated spot will hold the strips together until the remainder of the glue has set. It is necessary, however, that the` with glue lines at angles to each other with the same efficiency as the Linquist system provides fi a tingle 819.91m?- Two types of electrode systems are shown in Fig. 1 surrounding the rectangular beam i4. The electrodes shown at 20, 2|, and 22 are continuous integral encircling rings having flat sides, and are used when a large number of beams of the saine dimensions are to be manufactured. The high potential centraly electrode 2i! has side flares 24 and 25 on all four sides to provide a uniform high frequency field through the entire crosssectional area of the beams lli between the electrodes, as shown by the dotted lines in Fig. Z. Only one of the electrodes 2| and 22 may be used, but a better application of the generator energy is obtainable in the manner shown.

The other electrode system is of a similar nature, but is adjustable to accommodate diierently sized beams. A central high potential electrode Sil is provided with slots 3| and 32 and thumb screws 33 and 34, respectively, for tightening the electrodes in any adjusted position.

Similarly, electrode 31 has slots' 358 and 39 in the different sections thereof along with thumb nuts 4U and 4|, respectively, for tightening the electrede into different positions. The sections of the electrodes on the back and bottom surfaces of the beam i4 a-re also similarly provided with adjustable slots. If the beam were round, circular electrodes would be used.

Referring now to Fig. 2', a generator such as shown at 5B may be of thetype disclosed and claimed in copending U. S. applications of Frederick G. Albin, Ser. No. 540,767, iiled June 17, 1944, and Ser. No. 5603465-, led October 26, 1944, now Pat-ent No. 2,442,451, June 1, 1948. The electrodes 2| and 22 and electrodes 31 and M are grounded electrodes, while the central electrodes 20 and 30 with the ares 24, 25, 35, and 36, respectively, are the high potential electrodes. By extending the high potential electrode toward each grounded electrode with a slight substantially exponential outward curvature at an angle depending upon the separation between electrodes, but approximately fteen to thirty degrees to the axis of the beam I4, the semi-spherical elds, shown in Fig. 2` by the dotted lines, are produced. That is, in the example illustrated, two overlapping or intersecting fields will be directed through the beam |4` in each of two planes, the two fields being at right angles to one another and extending between regions adjacent the respective electrodes spaced along the lines oi intersection of the contacting surfaces.

The separation of',` or spacing between, the electrodes depends upon the larger dimension of the beam being glued. The general rule is that the distance between electrodes be twice the depth of the glueA line to be heated. This is illustrated in Fig. 2, where the distance ais at least twice that of distance b.

Thus, the glue lines between elements 5, 6, and 'I and between 8, 1, and ||l will be heated by the upper and lower sections of the electrodes in direct contact therewith, while the glue lines at right angles thereto, such as those between ele-l ments li and i2, i2 and E-'L and 9|U, and 5 and 8 will be heated by the fields produced by the opposite side sections of the electrodes. Thus, not only are equi-potential elds provided between the electrodes, but all'glu'e lines will receive the same degree of heating and all th'e glue will be set in the same period of time, thus safely pen mitting the removal ofl the clamps |6 and ilI` after' a short application of the high frequencyv energy.

' I claim:

1. A. system for heating the glue lines between adjacent surfaces of a plurality of pieces of lumber, said glue lines running at right angles to one another comprising a pair of clamps 4for clamping said pieces into a predetermined form, a high frequency generator, a rst electrode completely encircling and in contact with the periphery of said forni and. connected to said generator, and a second electrode completely encircling said form and connected to said generator, said second electrode being in contact with said form periphery at a distance from the center of said 'rst electrode which is twice the depth of the glue line to be heated, said second` electrode being flared away from said form in a direction toward said first electrode along a substantially exponential curve which is tangent to a plane at the region of contact of said second electrode with said form, said flare being at an angle of from iifteen degrees to thirty degrees with respect to said plane, said rst and second electrodes being dimensioned to substantially surround the portion of said form in which the glue lines are to be dried, and said first and second electrodes being adjustable to fit various beam sizes.

2. An electrode system for applying high frequency oscillations to glue between abutting lumber surfaces at angles to one another comprising means for applying pressure to said surfaces, a

pair of spaced electrodes encircling said lumber.

said electrodes contacting the edges of all of said abutting surfaces, and a third electrode posi# tioned between said' spaced electrodes, and encircling said lumber said third electrode being in contact with said lumber periphery and flaring away' from its region of' contact With said lumber upward in both directions toward said spaced electrodes along a substantially exponential curve which is tangent to a plane at the region of contact of said second electrode with said lumber, said flare being at an angle of between fifteen degrees and thirty degrees with respect to said plane, said spaced electrodes and said third electrode being dimensioned to substantially surround the portion of said lumber in which the glue lines are to be dried, said spaced electrodes and said third electrode being adjustable toY t various lumber sizes, and means for applying aradio frequency potential diierence between said third electrode and each electrode of said pair.

3. An electrode system for applying high fre-f quency oscillations tol glue lines angularly dis--` posed between the surfaces of a plurality of pieces of lumber tted to formv a beam, saidv system comprising a first electrode encircling and in contact with said beam periphery, and a second elec"- trode encircling said beam and in contact with said beam periphery at a distance from the center of said first electrode which is twice the depth of the glue line to be heated, said second electrode being flaredA away from said beam in a direction toward said iirst electrode along a substantially exponential curve whichy is tangent to a plane at the region of contact of said second electrode with said beam, said nare being at an 'i angle of from fteen degrees to thirty degrees' round the portionoi` said beam in which the glue lines are to be dried, and said first and secondi electrodes being adjustable to fit various beam..

sizes.

4. An electrode system for applying. high fr eg quency oscillations to glue lines angularly disposed between the surfaces of a plurality of pieces of lumber tted to forni a beam, said system comprising a pair of longitudinally spaced electrodes encircling and in contact with said beam periphn ery, a third electrode positioned between said spaced electrodes and encircling said beam, said third electrode being in contact with said beam periphery and aring away from its region of contact with said beam upward in both directions toward each of said spaced electrodes along a substantially exponential curve which is tangent to a plane at the region of `Contact of said second electrode with said beam, said are being at an angle of between fifteen degrees and thirty degrees with respect to said plane, said spaced electrodes and said third electrode being dimensioned to substantially surround the portion of 15 said beam in which the glue lines are to be dried, and said spaced electrodes and said third electrode being adjustable to fit various'beam sizes.

JOHN WATSON JONES, JR.

REFERENCES CITED The following references are of record in the ile of this patent:

UNITED STATES PATENTS 

